1.The mean temperature from the 9th to the 16th January, both days inclusive, was 11.6° C and from the 10th to the 17th it was 12.2° C. the temperature on the 9th was 10.8° C. What was it on the 17th?
(a) 15.6°C
(b) 4.8°C
(c) 9.6°C
(d) 15°C
Solution
(a); Total temperature from 9th to 16th of January =8×11.6°C=92.8°C
Total temperature from 10th to 17th of January =8×12.2=97.6°C
Now, according to the question,
Temperature on 17th of January =10.8°C+97.6°C-92.8°C=15.6°C
2.The weights of four rowers of a boat are respectively 71kg, 72 kg, 75 kg and 74 kg and the average weight of whole crew, including the coxswain is 76 kg. Find the weight of the coxswain.
(a) 88 kg
(b) 98 kg
(c) 68 kg
(d) 63 kg
Solution
(a); Required answer =5×76-(71+72+74+75)=88 kg
3.The average weight of 25 students was 36 kg. By the admission of a new student the average weight is reduced to 35.9 kg. The weight of the new student is
(a) 24.8 kg
(b) 20.8 kg
(c) 33.4 kg
(d) 21 kg
Solution; (c )
Weight of new student =(26×35.9-25×36)=33.4 kg
4.The average of 60 numbers is 38. If two numbers namely, 45 and 55 are discarded, the average of remaining numbers is:
(a) 56.61
(b) 44.76
(c) 45.41
(d) 46.81
Solution
(c); Total of 50 numbers =60×38=2280
Average of 48 numbers =(2280-(45+55))/48=2180/48=45.41
5.The average age of an adult class is 40 years. 12 new students with an average age of 32 years join the class, thereby decreasing the average of the class by 4 years. The original strength of the class was:
(a) 10
(b) 11
(c) 12
(d) 15
Solution; (c)
40x+12×32=(12+x)×36
∴ x=12
6.The average expenditure of a man for the first five months is RS. 120 and for the next seven months is Rs. 130. His monthly average income if he saves Rs. 290 in that year, is:
(a) Rs. 160
(b) Rs. 170
(c) Rs. 150
(d) Rs. 140
Solution.(c)
5*120+7*130= 600+910
=1510+290
=1800/12= 150
7.A cricketer scored 190 runs in the first test and 358 runs in the second. How many runs should he score in the third test so that his average score in the three tests would be 360 runs?
(a) 219
(b) 242
(c) 334
(d) None of these
Solution (d); Let the runs he should score in third test be x.
Then,
(190+358+x)/3=360⇒532
8.The average salary of 21 workers in an office is Rs. 1700 per month. If the manager’s salary is added, the average becomes Rs. 3000 per month. The manager’s annual salary (in Rs.) is:
(a) 24000
(b) 25200
(c) 45600
(d) None of these
Solution
(d); Total monthly salary of 21 personnels = Rs. (22×3000)= Rs. 66000.
Total monthly salary of 20 personnels = Rs.(21×1700)= Rs. 35700.
Monthly salary of the managers = Rs. 30300
Annual salary of the manager = Rs. 363600
9.In a coconut grove, (x+2) trees yields 60 nuts per year, x trees yield 120 nuts per year and (x-2) trees yield 180 nuts per year. If the average yield per year per tree be 100, find x.
(a) 4
(b) 2
(c) 8
(d) 6
Solution (a); ((x+2)×60+x×120+(x-2)×180)/(x+2+x+x-2)=100
∴x=4
10.The average age of students in section A of 50 students is 14 years and the average age of students in section B of 30 students is 6 years. Find the average age of students in both sections taken together.
(a) 11
(b) 13
(c) 12
(d) 14
Solution: (a)
we have the required average =(50×14+30×6)/(50+30)=11 years
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